Sheet stacking device and image forming system

Abstract

To improve accuracy of height adjustment of a stacking tray.SOLUTION: A sheet stacking device includes an ejection unit for ejecting sheets, a stacking tray 61 on which the sheets ejected by the ejection unit are stacked, an elevating mechanism 63 for raising and lowering the stacking tray 61, a tray detection unit 71 capable of continuously detecting the height of the stacking tray 61 over the entire elevation range of the stacking tray 61, and a control unit for controlling the elevation of the stacking tray 61 based on the detection result of the tray detection unit 71. The tray detection unit 71 is a contact image sensor in which a plurality of photoelectric conversion elements are arranged in the elevation direction of the stacking tray 61.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a sheet stacking device for stacking discharged sheets and an image forming system. [Background technology]

[0002] Sheet stacking devices are known that stack sheets on which images have been formed by an image forming apparatus. The sheet stacking device includes, for example, a discharge section (discharge rollers, etc.) that discharges sheets, a stacking tray on which the discharged sheets are stacked, and a lifting mechanism that raises and lowers the stacking tray depending on the amount of stacked sheets. Also known is a post-processing device that includes a post-processing section that performs post-processing on sheets on which images have been formed, and the sheet stacking device that stacks the post-processed sheets.

[0003] In such sheet stacking devices, if the top surfaces of the stacked sheets are too low relative to the discharge section, the position and posture of the discharged sheets will be disturbed, making it difficult for the user to align the documents removed from the discharge tray. On the other hand, if the top surfaces of the sheets are too close to the discharge section, the stacked sheets and the discharged sheets will interfere with each other. Therefore, technologies for maintaining the appropriate height of the stacking tray have been studied.

[0004] For example, Patent Document 1 describes a method in which a swingable detection lever detects the height of the topmost sheet by contacting it with the surface of the sheet, and a tray lifting device is driven to displace the paper output tray so as to maintain that position at a constant height. Patent Document 2 describes a method in which a motor rotation speed detection means is provided on the output shaft of a motor that serves as the drive source for the tray lifting mechanism, the amount of paper loaded on the tray is detected based on the rotation speed detection result, and the tray position is set based on the amount of paper loaded. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-9137 [Patent Document 2] Japanese Patent Application Publication No. 9-255212 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with the configuration described in Patent Document 1, there is a risk that the detection lever may get in the way or be damaged when the user removes sheets from the tray. With the configuration described in Patent Document 2, the repeated rising and falling during actual operation complicates control, raising the risk of falsely detecting the load amount, making it difficult to improve the accuracy of stack tray height adjustment. Also, if the power is turned on with sheets stacked, the position of the stack tray cannot be recognized, making it impossible to adjust the stack tray height.

[0007] Furthermore, the amount of sheets that can be loaded without compromising alignment (the alignment of the sheet position and posture) varies depending on the conditions of the print job. For example, when comparing large and small sheets, even if the number of sheets is the same, the smaller size is more likely to be unstable. Also, because the thickness of the sheet stack increases near stapled sections and folds, the tilt of the sheet stack increases as the load increases. Furthermore, when sheets of different sizes are mixed, the thickness of the sheet stack varies depending on the location, causing tilt. In these cases, as the load increases, the sheet alignment decreases, and sheets may collapse and fall.

[0008] SUMMARY OF THE INVENTION In consideration of the above circumstances, an object of the present invention is to provide a sheet stacking device and an image forming system that can improve the accuracy of height adjustment of the stacking tray. [Means for solving the problem]

[0009] In order to solve the above problem, the sheet stacking device of the present invention is characterized by comprising a discharge section that discharges sheets, a stacking tray on which the sheets discharged by the discharge section are stacked, a lifting mechanism that raises and lowers the stacking tray, a first detection section that can continuously detect the height of the stacking tray throughout the entire lifting range of the stacking tray, and a control section that controls the lifting and lowering of the stacking tray based on the detection result of the first detection section.

[0010] The first detection unit may be a contact image sensor in which a plurality of photoelectric conversion elements are arranged in the direction in which the loading tray is raised and lowered.

[0011] The sheet loading device may further include a second detection unit that detects whether the loading surface of the loading tray on which the sheets are loaded is positioned at a receiving position for receiving the sheets, and the control unit may be configured to lower the loading tray according to the amount of sheets loaded and position the loading surface at the receiving position based on the detection result of the loading surface by the second detection unit, detect the height of the loading tray when the loading surface is positioned at the receiving position using the first detection unit, and execute full-load control to stop the lifting and lowering of the loading tray when the height of the loading tray reaches a predetermined lower limit position.

[0012] In addition, the image forming system of the present invention includes an image forming device that accepts a print job and forms an image on the sheet, a sheet stacking device as described in claim 3 that stacks the sheet discharged from the image forming device, and a memory unit that stores condition data indicating the conditions included in the print job and the lower limit position of the height of the stacking tray in association with each other, and the control unit is characterized in that, during the full control, when the stacking tray reaches the lower limit position associated with the condition data corresponding to the print job being processed, it stops the lifting and lowering of the stacking tray and interrupts the print job.

[0013] The control unit may interrupt the print job using the lower limit position associated with the stored condition data when the condition data included in the print job being processed matches the condition data stored in the memory unit at a certain rate.

[0014] The image forming system may include an operation unit that accepts operations, and the control unit may be configured to, when the operation unit accepts an operation to store the lower limit position of the height of the loading tray, associate condition data indicating the conditions included in the print job being processed with the height of the loading tray detected by the first detection unit and store them in the memory unit.

[0015] The control unit may also notify the user that it is recommended to set the lower limit position of the height of the loading tray relative to the operation unit when condition data corresponding to the print job being processed is not stored in the memory unit.

[0016] The control unit may interrupt the print job using the lower limit position only when a load limit mode that limits the amount of sheets that can be loaded is set.

[0017] The image forming system may include a post-processing unit that performs one or more of stapling, shifting, and center-folding on the sheets on which images have been formed, and the conditions included in the print job may include one or more of the presence or absence and number of staples, the presence or absence of shifting, the presence or absence of center-folding, and the number of sheets that make up a copy of the sheet stack.

[0018] The conditions included in the print job may include one or more of the size of the sheets and whether or not mixed sizes are used. [Effects of the Invention]

[0019] According to the present invention, the accuracy of adjusting the height of the stacking tray can be improved. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view showing the appearance of an image forming system according to an embodiment of the present invention; [Figure 2] 1 is a front view schematically illustrating an internal configuration of a post-processing device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a perspective view of a lifting mechanism according to an embodiment of the present invention. [Figure 4] FIG. 2 is a front view of the lifting mechanism according to the embodiment of the present invention. [Figure 5] 1 is a block diagram showing an electrical configuration of an image forming system according to an embodiment of the present invention. [Figure 6] 4 is a flowchart showing the operation of the sheet stacking device according to the embodiment of the present invention. [Figure 7] FIG. 10 is a diagram showing a tray height setting screen according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] An image forming system 100 according to an embodiment of the present invention will be described below with reference to the drawings.

[0022] First, the overall configuration of image forming system 100 will be described. Fig. 1 is a perspective view showing the appearance of image forming system 100. In the following description, the Fr side in Fig. 1 is the front side (front side) of image forming system 100, and the left and right directions will be described based on the direction when image forming system 100 is viewed from the front. In each figure, U, Lo, L, R, Fr, and Rr represent up, down, left, right, front, and rear, respectively.

[0023] The image forming system 100 includes an image forming apparatus 1 and a post-processing device 110. The image forming apparatus 1 is, for example, a multifunction device including a printer, a scanner, and a document transport device. The document transport device transports a document along a transport path that passes through the reading position of the scanner. The scanner is a flatbed image scanner that reads a document and generates image data. The printer forms an image on a sheet using an inkjet method, an electrophotographic method, or the like. The post-processing device 110 performs post-processing on the sheet transported from the printer and discharges the sheet.

[0024] Next, the configuration of the post-processing device 110 will be described (see FIGS. 1 and 2). FIG. 2 is a front view schematically showing the internal configuration of the post-processing device 110. The post-processing device 110 has a roughly rectangular parallelepiped housing 21. An inlet 22 is provided at the top of the right side plate of the housing 21 to receive sheets conveyed from the image forming device 1.

[0025] A recess 23 recessed to the right is provided in the left side plate of the housing 21. When viewed from the left, the recess 23 is generally rectangular with a long side extending in the up-down direction and a short side extending in the front-to-rear direction. The recess 23 includes a bottom 23B formed to the right of the left side plate, front and rear side walls 23S formed between the front and rear ends of the bottom 23B and the left side plate, an upper wall 23U formed between the upper end of the bottom 23B and the left side plate, and a lower wall 23L formed between the lower end of the bottom 23B and the left side plate.

[0026] A discharge section 31 for discharging sheets is provided above the recess 23. A sheet stacking device 120, which will be described later, is provided below the discharge section 31. An upper discharge section 44 is provided on the top plate of the housing 21. A transport path 41 is provided inside the housing 21, from the receiving opening 22 to the discharge section 31, and a branch path 42 is provided that branches off from the transport path 41 and leads to the upper discharge section 44. A transport roller 43 is provided on the transport path 41.

[0027] The upper discharge section 44 includes a discharge roller and a discharge port. A fixed-position stacking tray 45 is provided on the left side of the upper discharge section 44.

[0028] The discharge section 31 includes a discharge opening 32 and a discharge roller 33 provided to the right of the discharge opening 32. The discharge roller 33 includes a drive roller 33D driven by a motor (not shown) and a driven roller 33N that follows the drive roller 33D. The drive roller 33D can be pressed against and separated from the driven roller 33N.

[0029] Below the conveying path 41, there are provided a processing tray 51 (an example of a post-processing section) and a stapler 54 (an example of a post-processing section). The processing tray 51 is provided so as to incline downward from the discharge port 32 to the right, and a sheet stack to be stapled by the stapler 54 is stacked on the processing tray 51. The left end of the processing tray 51 rotatably supports the driven roller 33N of the discharge roller 33. The stapler 54 is provided to the right of the processing tray 51, and staples the right end of the sheet stack stacked on the processing tray 51 (stapling process). The post-processing section 110 may also be provided with a center-folding device (an example of a post-processing section) that folds sheets in the middle (not shown).

[0030] The processing tray 51 is provided with a pair of side fences 52 facing each other in the front-rear direction. The pair of side fences 52 are movable in the sheet width direction (direction intersecting with the discharge direction Y). The pair of side fences 52 move synchronously in directions approaching each other, thereby aligning the sheets on the processing tray 51 in the width direction. Furthermore, the pair of side fences 52 move together in the width direction, thereby moving the sheet stack in the width direction (shift processing). A sheet receiving plate 53 is provided at the right end of the processing tray 51. The right end of the sheet stack stacked on the processing tray 51 comes into contact with the sheet receiving plate 53, thereby aligning the sheets in the discharge direction Y.

[0031] [Sheet stacking device] Next, a description will be given of the configuration of the sheet stacking device 120. Fig. 3 is a perspective view of the lifting mechanism 63. Fig. 4 is a front view of the lifting mechanism 63.

[0032] The sheet stacking device 120 includes a discharge section 31 that discharges sheets, a stacking tray 61 on which the sheets discharged by the discharge section 31 are stacked, a lifting mechanism 63 that raises and lowers the stacking tray 61, a tray detection section 71 that can continuously detect the height of the stacking tray 61 throughout the entire lifting range of the stacking tray 61, and a control section 2 that controls the raising and lowering of the stacking tray 61 based on the detection results of the tray detection section 71.

[0033] [Loading tray] The top surface of the stacking tray 61 is inclined upward toward the downstream side in the sheet discharge direction Y. The stacking tray 61 is provided to the left of the recessed portion 23. Brackets 62 that connect the stacking tray 61 to a belt 66 (described later) are provided at the right end portions of the front and rear side surfaces of the stacking tray 61 (see FIGS. 3 and 4). Slits (not shown) are formed in the vertical direction at locations corresponding to the brackets 62 on the bottom 23B or side wall 23S of the recessed portion 23, and the brackets 62 pass through the slits.

[0034] [Lifting mechanism] The lifting mechanism 63 (see FIGS. 3 and 4) includes a drive shaft 64, a driven shaft 65 provided below the drive shaft 64, and belts 66 provided at two locations, front and rear. The lifting mechanism 63 is provided to the right of the recessed portion 23. Sprockets 64S are provided at two locations, front and rear, of the drive shaft 64, and a drive gear 64G is provided at one end of the drive shaft 64. Driving force is transmitted to the drive gear 64G via a motor and a reduction gear train (not shown). Sprockets 65S are provided at two locations on the driven shaft 65 corresponding to the sprocket 64S of the drive shaft 64. An endless belt 66 with teeth formed on its inner peripheral surface is wound around the sprocket 64S of the drive shaft 64 and the sprocket 65S of the driven shaft 65. A bracket 62 of the stacking tray 61 is fixed to the outer peripheral surface of the belt 66. When a driving force is transmitted to the driving gear 64G, the front and rear belts 66 circulate in the same direction in synchronization, and the loading tray 61 moves up and down as the belts 66 move.

[0035] [Top surface detection unit (second detection unit)] An upper surface detection unit 68 (an example of a second detection unit) is provided on the upper portion of the recess 23 of the housing 21 (see FIG. 2). The upper surface detection unit 68 is, for example, a transmission type, a reflection type, or other optical sensor. In the case of a transmission type, a light emitting unit is provided on one of the front and rear side walls 23S of the recess 23, and a light receiving unit is provided on the other side wall 23S (not shown). In the case of a reflection type, a light emitting unit and a light receiving unit are provided on one side wall 23S, and a reflecting mirror is provided on the other side wall 23S (not shown).

[0036] The top surface detection unit 68 detects whether the stacking surface on which sheets are stacked is positioned at a receiving position for receiving sheets. Specifically, the stacking surface refers to the top surface of the sheets stacked on the stacking tray 61 (the top surface of the uppermost sheet), or the top surface of the stacking tray 61 when no sheets are stacked. If the height of the stacking surface is equal to or greater than the height of the optical path of the light-emitting unit, the light is blocked by the sheets or the stacking tray 61, and the light-receiving unit cannot receive the light. In this case, the top surface detection unit 68 outputs a first-level signal (hereinafter referred to as a light-blocking signal). On the other hand, if the height of the stacking surface is less than the height of the optical path of the light-emitting unit, the light is not blocked by the sheets or the stacking tray 61, and the light-receiving unit receives the light. In this case, the top surface detection unit 68 outputs a second-level signal (hereinafter referred to as a light-receiving signal).

[0037] The receiving position is a position where the right end of the stacking surface is spaced a predetermined distance downward from the discharge opening 32 of the discharge section 31. This distance is set to minimize interference between the discharged sheets and the stacking surface, a decrease in the alignment of the discharged sheets, and other problems. The control section 2, which will be described later, executes top surface height control at a predetermined timing using the detection result of the stacking surface by the top surface detection section 68. The top surface height control will be described in detail later.

[0038] [Tray detection unit (first detection unit)] A tray detector 71 (an example of a first detector) capable of continuously detecting the height of the loading tray 61 throughout the entire lifting range of the loading tray 61 is provided to the right of either the front or rear belt 66 (see FIG. 4). A detection piece 72 protruding to the right is provided on the bracket 62 of the loading tray 61. The tray detector 71 is a line sensor including a plurality of photoelectric conversion elements arranged in the lifting direction of the loading tray 61. The tray detector 71 is, for example, a CIS (Contact Image Sensor) including a light source, a rod lens array, and a CMOS (Complementary Metal-Oxide-Semiconductor Field-Effect Transistor) image sensor (not shown). A large number of CMOS image sensors are arranged throughout the entire lifting range of the loading tray 61. The light source includes an LED (Light Emitting Diode) provided at the upper or lower end of the lifting range of the loading tray 61 and a light guide that guides the LED light to the detection piece 72. In other words, the range in which the first detection unit can detect the height of the loading tray 61 is continuous throughout the entire range in which the loading tray 61 can be raised and lowered.

[0039] [Electrical configuration] FIG. 5 is a block diagram showing the electrical configuration of the image forming system 100. The image forming apparatus 1 is provided with a control unit 2. The control unit 2 includes a calculation unit 2P and a storage unit 2M. The calculation unit 2P is, for example, a CPU (Central Processing Unit). The storage unit 2M includes storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an EEPROM (Electrically Erasable Programmable Read Only Memory). The calculation unit 2P performs various processes by reading and executing control programs stored in the storage unit 2M. Note that the control unit 2 may be realized by an integrated circuit without using software.

[0040] The control unit 2 is connected to an upper surface detection unit 68, a tray detection unit 71, a lifting mechanism 63, and an operation unit 19. The operation unit 19 is provided at the upper front portion of the image forming apparatus 1 (see FIG. 1). The operation unit 19 includes a display panel, a touch panel provided on top of the display surface of the display panel, and a keypad adjacent to the display panel (not shown). The control unit 2 displays a screen showing operation menus for the image forming apparatus 1 and the post-processing device 110 on the display panel, and controls each unit of the image forming apparatus 1 and the post-processing device 110 in response to operations detected by the touch panel and the keypad.

[0041] Here, the load amount limit mode will be described. The load amount limit mode is a mode that prevents the integrity of the stacked sheets from deteriorating by limiting the load amount according to the conditions of the print job. Specifically, condition data indicating the conditions included in the print job and the lowest height limit of the stacking tray 61 at which sheets can be stacked without deteriorating integrity are associated and stored in the memory unit 2M. The condition data includes, for example, six items: sheet size, whether or not mixed sizes are used, whether and how many staples are used, whether or not shift processing is used, whether or not center folding is used, and the number of sheets that make up one sheet bundle.

[0042] The sheet size can be set to one of four types: A4 or Letter, A4R or LetterR, B4 or Legal, and Ledger or A3. Of these, A4R or LetterR means that the long side of A4 or Letter is conveyed parallel to the conveying direction. The other three types all mean that the short side is conveyed parallel to the conveying direction.

[0043] Mixed size loading means that multiple types of sheets of different sizes are transported in one print job, and this can be set to "yes" or "no."

[0044] Stapling refers to binding multiple sheets together using the staple device 54. The number of staples refers to the number of locations where staples are applied to one sheet stack. The presence or absence of staples and the number of locations can be set to two, one, or none.

[0045] The shift process means a process of shifting the sheet stack alternately in the width direction one by one by moving the pair of side fences 52 together in the width direction, and can be set to be enabled or disabled.

[0046] The center folding process refers to a process of folding a sheet bundle in the middle using a center folding device, and can be set to ON or OFF.

[0047] The number of sheets constituting one set of sheets is the number of sheets constituting the sheet bundle in the stapling process, shift process, and center folding process, and can be set to 1, 2, 3 to 10, or 11 or more.

[0048] The memory unit 2M stores a data table that associates these condition data with the lowest height position of the stacking tray 61 at which sheets can be stacked without compromising consistency. The data table is stored, for example, by the manufacturer before shipping from the factory. The manufacturer conducts experiments using the sheet stacking device 120 with various combinations of the above condition data items to determine the lowest height position of the stacking tray 61 at which sheets can be stacked without compromising consistency. The degree of consistency corresponding to the lowest position is, for example, a level at which the tilt of the stacked sheets cannot be visually confirmed. The manufacturer writes the lowest position determined through the experiment into the memory unit 2M in association with the condition data. In this case, it is desirable to store multiple sets of combinations of condition data and lowest positions that are expected to be used relatively frequently.

[0049] The condition data and the lower limit position may also be stored by the user, as will be described later.

[0050] The load limit mode can be set and canceled at any time. When the operation menu of the post-processing device 110 is called up on the operation unit 19, a selection button for selecting the load limit mode and a cancellation button for canceling the load limit mode are displayed in one corner of the screen (not shown). In the initial state, the load limit mode is canceled.

[0051] Next, a description will be given of the operation of the sheet stacking device 120. Fig. 6 is a flowchart showing the operation of the sheet stacking device 120. When the image forming system 100 is powered on, the control unit 2 executes full-stack control in accordance with the flowchart in Fig. 6.

[0052] First, the control unit 2 determines whether a print job has started (step S01). If it determines that a print job has not started (step S01: NO), the control unit 2 repeats the process of step S01. On the other hand, if it determines that a print job has started (step S01: YES), the control unit 2 determines whether the load amount limit mode has been selected (step S03). If the load amount selection mode has been selected (step S03: YES), the control unit 2 proceeds to the process of step S05. If the load amount selection mode has not been selected (step S03: NO), the control unit 2 proceeds to the process of step S09. In this case, the lower limit position of the height of the stacking tray 61 for the print job being processed is set to an initial value. The initial value is the lowest height to which the stacking tray 61 can be lowered by the lifting mechanism 63.

[0053] In step S05, the control unit 2 determines whether condition data corresponding to the print job is stored in the storage unit 2M. Specifically, the control unit 2 compares the conditions included in the print job being processed with the condition data stored in the storage unit 2M, and extracts condition data that matches a predetermined number or a predetermined percentage of the conditions included in the print job being processed. Here, the predetermined number is, for example, five of the six conditions described above. The predetermined percentage is, for example, 80%.

[0054] If condition data that matches a predetermined number or a predetermined percentage of the conditions included in the print job being processed is stored in the storage unit 2M, the control unit 2 determines that the condition data corresponding to the print job is stored in the storage unit 2M (step S05: YES), and proceeds to the processing of step S07. On the other hand, if condition data that matches a predetermined number or a predetermined percentage of the conditions is not stored in the storage unit 2M, the control unit 2 determines that the condition data corresponding to the print job is not stored in the storage unit 2M (step S05: NO), and proceeds to the processing of step S21.

[0055] In step S07, the control unit 2 sets the lower limit position associated with the condition data. Specifically, the control unit 2 sets the lower limit position associated with the condition data extracted in step S05 as the lower limit position of the height of the stacking tray 61 for the print job being processed.

[0056] Next, the control unit 2 starts the upper surface height control (step S09). Specifically, the control unit 2 checks the output of the upper surface detection unit 68 each time the discharge unit 31 discharges a predetermined number of sheets. If the height of the stacking surface is equal to or greater than the height of the optical path of the upper surface detection unit 68, the upper surface detection unit 68 outputs a light-blocking signal. On the other hand, if the height of the stacking surface is less than the height of the optical path of the upper surface detection unit 68, the upper surface detection unit 68 outputs a light-receiving signal. As the discharge of sheets is repeated, the height of the stacking surface gradually increases, and the light-receiving signal switches to a light-blocking signal. When the light-receiving signal switches to a light-blocking signal, the control unit 2 lowers the stacking tray 61 until the upper surface detection unit 68 outputs a light-receiving signal, and then raises the stacking tray 61 until the upper surface detection unit 68 outputs a light-blocking signal. This process maintains the height of the stacking surface within a predetermined range including the receiving position, so that the distance between the discharge opening 32 of the discharge unit 31 and the stacking surface is maintained within an appropriate range. The control unit 2 continues to control the upper surface height while the discharge unit 31 is discharging the sheets.

[0057] Next, the control unit 2 determines whether the print job has ended (step S11). If it has determined that the print job has ended (step S11: YES), the control unit 2 repeats the processes from step S01 onwards. On the other hand, if it has determined that the print job has not ended (step S11: NO), the control unit 2 determines whether the height of the stacking tray 61 has reached the lowest position (step S13). Specifically, the control unit 2 determines whether the height of the stacking tray 61 detected by the tray detection unit 71 has reached the lowest position set in step S07. If it has determined that the height of the stacking tray 61 has not reached the lowest position (step S13: NO), the control unit 2 repeats the processes from step S11 onwards.

[0058] On the other hand, if it is determined that the height of the stacking tray 61 has reached the lower limit position (step S13: YES), the control unit 2 stops the lifting and lowering of the stacking tray, suspends the print job (step S15), and causes the operation unit 19 to display a message urging the user to remove the printed materials and a resume button for resuming the print job. The resume button can be operated only when the upper surface detection unit 68 is outputting a light reception signal.

[0059] Next, the control unit 2 determines whether the print job has been resumed (step S17). Specifically, if the resume button has not been operated, the control unit 2 determines that the print job has not been resumed (step S17: NO) and repeats the process of step S17. On the other hand, if the resume button has been operated, the control unit 2 determines that the print job has been resumed (step S17: YES) and repeats the process from step S09 onwards.

[0060] Next, the processing from step S21 onwards will be described. In step S21, the control unit 2 causes the operation unit 19 to display a tray height setting screen. FIG. 7 is a diagram showing the tray height setting screen. The tray height setting screen includes the above six conditions included in the print job and a tray height setting button for setting the height of the stacking tray 61. In this example, the sheet size is A4 or Letter. Mixed size loading, shift processing, and center folding processing are performed. Stapling is performed in two places. The number of sheets that make up one sheet stack is 3 to 10.

[0061] The tray height setting screen may also include a message recommending that the user set the lower limit position of the height of the loading tray 61 (for example, "Please use the tray height setting button to set the lower limit position of the tray corresponding to the print job being processed").

[0062] Next, the control unit 2 starts the upper surface height control in the same way as in step S09 (step S23). Next, the control unit 2 determines whether the print job has ended in the same way as in step S11 (step S25).

[0063] Next, the control unit 2 determines whether the lower limit position of the height of the stacking tray 61 has been set (step S27). Specifically, the user observes the state of the sheets stacked on the stacking tray 61, and if the user detects signs of a decrease in consistency, the user operates the tray height setting button. If the setting button on the tray height setting screen has not been operated, the control unit 2 determines that the lower limit position has not been set (step S27: NO) and repeats the processing from step S25 onwards. On the other hand, if the setting button on the tray height setting screen has been operated, the control unit 2 determines that the lower limit position has been set (step S27: NO) and interrupts the print job (step S29). At this time, the control unit 2 associates the height of the stacking tray 61 detected by the tray detection unit 71 with condition data indicating the conditions included in the print job being processed and stores the height in the memory unit 2M.

[0064] Next, the control unit 2 determines whether the print job has been resumed (step S31). Specifically, if the resume button has not been operated, the control unit 2 determines that the print job has not been resumed (step S31: NO) and repeats the process of step S31. On the other hand, if the resume button has been operated, the control unit 2 determines that the print job has been resumed (step S31: YES) and repeats the process from step S23 onwards.

[0065] The sheet stacking device 120 according to the present embodiment described above includes a discharge section 31 that discharges sheets, a stacking tray 61 on which the sheets discharged by the discharge section 31 are stacked, a lifting mechanism 63 that raises and lowers the stacking tray 61, a first detection section (tray detection section 71) that can continuously detect the height of the stacking tray 61 throughout the entire lifting range of the stacking tray 61, and a control section 2 that controls the lifting and lowering of the stacking tray 61 based on the detection results of the first detection section, thereby improving the accuracy of height adjustment of the stacking tray 61.

[0066] Furthermore, according to the sheet stacking device 120 of this embodiment, the first detection unit is a contact image sensor in which multiple photoelectric conversion elements are arranged in the lifting and lowering direction of the stacking tray 61, so that the height of the stacking tray 61 can be quickly detected when the power is turned on or when returning from power saving mode.

[0067] Furthermore, the sheet stacking device 120 according to this embodiment is further provided with a second detection unit (upper surface detection unit 68) that detects whether the loading surface on which sheets are loaded of the loading tray 61 is positioned at the receiving position for receiving the sheets, and the control unit 2 lowers the loading tray 61 according to the amount of sheets loaded based on the detection result of the loading surface by the second detection unit, and positions the loading surface at the receiving position, and detects the height of the loading tray 61 with the loading surface positioned at the receiving position using the first detection unit, and when the height of the loading tray 61 reaches a predetermined lower limit position, executes full-load control to stop the lifting and lowering of the loading tray 61, so that the loading surface can always be positioned at the receiving position.

[0068] Furthermore, the image forming system 100 according to this embodiment includes an image forming apparatus 1 that accepts a print job and forms an image on a sheet, a sheet stacking device 120 that stacks sheets discharged from the image forming apparatus 1, and a storage unit 2M that stores condition data indicating the conditions included in the print job and the lowest height limit of the stacking tray 61 in association with each other. During full-stack control, the control unit 2 stops the lifting and lowering of the stacking tray 61 and interrupts the print job when the stacking tray 61 reaches the lowest limit associated with the condition data corresponding to the print job being processed. This allows the print job to be interrupted before the integrity of the stacked sheets deteriorates. As a result, the maximum number of sheets can be stacked without deteriorating the integrity. Furthermore, sheets can be prevented from falling off the stacking tray 61. Furthermore, the effort required to align sheets removed from the stacking tray 61 can be reduced.

[0069] Furthermore, according to the image forming system 100 of this embodiment, when the condition data included in the print job being processed matches the condition data stored in the memory unit 2M to a certain extent, the control unit 2 interrupts the print job using the lower limit position associated with the stored condition data. Therefore, even if there is no condition data stored that perfectly matches the conditions included in the print job being processed, the load amount can be limited using the lower limit position associated with condition data that is close to the conditions included in the print job.

[0070] Furthermore, the image forming system 100 according to this embodiment is provided with an operation unit 19 that accepts operations, and when the operation unit 19 accepts an operation to store the lower limit position of the height of the loading tray 61, the control unit 2 associates the condition data indicating the conditions included in the print job being processed with the height of the loading tray 61 detected by the first detection unit and stores them in the memory unit 2M, so that the lower limit position can be stored based on the judgment made by the user when observing the loading situation.

[0071] Furthermore, according to the image forming system 100 of this embodiment, when the condition data corresponding to the print job being processed is not stored in the memory unit 2M, the control unit 2 notifies the user that it is recommended to set the lower limit position of the height of the stacking tray 61 relative to the operation unit 19, thereby making the user aware of the need to perform the operation to store the lower limit position.

[0072] Furthermore, according to the image forming system 100 of this embodiment, the control unit 2 interrupts the print job using the lower limit position only when a load capacity limit mode that limits the sheet load capacity is set, so that the load capacity can be limited only when the user determines that a load capacity limit is necessary.

[0073] Furthermore, the image forming system 100 according to this embodiment is provided with a post-processing device 110 that performs post-processing on sheets on which images have been formed, including one or more of stapling, shifting, and center-folding, and the conditions included in the print job include one or more of the presence or absence and number of staples, presence or absence of shifting, presence or absence of center-folding, and the number of sheets that make up a sheet stack, so that the load capacity can be limited depending on the post-processing conditions.

[0074] Furthermore, according to the image forming system 100 of this embodiment, the conditions included in the print job include one or more of the sheet size and whether or not mixed sizes are used, so that the load amount can be limited depending on the sheet size and whether or not mixed sizes are used.

[0075] The above embodiment may be modified as follows.

[0076] In the above embodiment, an example was shown in which the control unit 2 suspends the print job (step S29) when it is determined that the lower limit position for the height of the stacking tray 61 has been set (step S27: YES). However, in addition to this, the configuration may also allow the user to suspend the print job using the operation unit 19 and then set the lower limit position. This configuration is also suitable for cases in which the user is slow to detect signs of a decrease in alignment. For example, if the tilt of the stacked sheets becomes significant or if the upper sheet falls, the user may suspend the print job, remove sheets until the tilt is resolved, and then operate the tray height setting button.

[0077] The sheet stacking device 120 or the post-processing device 110 may have the functions of the control unit 2, the storage unit 2M, and the operation unit 19 that the image forming apparatus 1 according to the above embodiment has.

[0078] In the above embodiment, an example is shown in which a CIS is used as the tray detection unit 71, but instead of a CIS, the height of the loading tray 61 may be detected by a sensor that irradiates light onto the detection piece 72 from above or below and detects the distance to the detection piece 72 from the phase shift of the reflected light from the detection piece 72. [Explanation of symbols]

[0079] 100 Image forming system 1. Image forming device 120 Sheet stacking device 2. Control Unit 2M storage section 19 Control section 31 Discharge section 51 Processing tray (post-processing section) 54 Stapling device (post-processing section) 61 Loading tray 63 Lifting mechanism 68 Upper surface detection unit (second detection unit) 71 Tray detector (first detector)

Claims

1. an image forming device that receives a print job and forms an image on a sheet; a discharge section for discharging the sheet; a stacking tray on which the sheets discharged by the discharge unit are stacked; a lifting mechanism for lifting and lowering the loading tray; a first detection unit capable of continuously detecting the height of the loading tray throughout the entire lifting range of the loading tray; a control unit that controls the lifting and lowering of the stacking tray based on a detection result of the first detection unit; a second detection unit that detects whether a loading surface of the loading tray on which the sheets are loaded is positioned at a receiving position for receiving the sheets; a storage unit that stores condition data indicating conditions included in the print job and a lower limit position of the height of the stacking tray in association with each other; an operation unit that accepts an operation, The control unit based on a detection result of the loading surface by the second detection unit, the loading tray is lowered in accordance with the loading amount of the sheets, and the loading surface is disposed at the receiving position; a first detection unit detecting a height of the loading tray when the loading surface is placed at the receiving position, and when the height of the loading tray reaches the lower limit position, executing a full-load control to stop lifting and lowering of the loading tray; In the full-fill control, when the stacking tray reaches the lower limit position associated with the condition data corresponding to the print job being processed, the lifting and lowering of the stacking tray is stopped, and the print job is interrupted; An image forming system characterized in that when the operation unit receives an operation to store the lower limit position of the height of the loading tray while the loading tray is being lowered during processing of the print job, the condition data indicating the conditions included in the print job being processed and the height of the loading tray detected by the first detection unit are associated and stored in the memory unit.

2. 2. The image forming system according to claim 1, wherein the first detection unit is a contact image sensor in which a plurality of photoelectric conversion elements are arranged in the direction in which the stacking tray is raised and lowered.

3. The image forming system described in claim 1 or 2, characterized in that the control unit interrupts the print job using the lower limit position associated with the stored condition data when the condition data included in the print job being processed matches the condition data stored in the memory unit at a certain rate.

4. The image forming system of any one of claims 1 to 3, characterized in that when the condition data corresponding to the print job being processed is not stored in the memory unit, the control unit notifies the user that it is recommended to perform an operation to set the lower limit position of the height of the loading tray relative to the operation unit.

5. The image forming system according to any one of claims 1 to 4, characterized in that the control unit interrupts the print job using the lower limit position only when a load limit mode that limits the load amount of the sheets is set.

6. a post-processing unit that performs one or more of a staple process, a shift process, and a center-fold process on the sheet on which the image has been formed; An image forming system according to any one of claims 1 to 5, characterized in that the conditions included in the print job include one or more of the presence or absence and number of staple processing, the presence or absence of shift processing, the presence or absence of center folding processing, and the number of sheets constituting a copy of the sheet stack.

7. 7. The image forming system according to claim 1, wherein the conditions included in the print job include at least one of the size of the sheets and whether or not mixed sizes are used.

Images